Ultrastructure of the periductal area of comedo carcinoma in situ of the breast

We have previously shown that the different biological natures of comedo du ctal carcinoma in situ (DCIS) and non-comedo DCIS may, in part, be explaine d by the different expression patterns of tenascin, a large extracellular m atrix protein, as observed by immunohistochemical studies. In the present s tudy, we compared 8 cases of comedo DCIS with 5 cases of non-comedo DCIS by ultrastructural analysis, focusing on the myoepithelium, basal lamina, and tenascin-positive extracellular periductal stromal matrix. Our observation s show that the comedo type DCIS frequently has an altered basal lamina, a looser and more disorganized collagenous matrix, and a general increase in stromal cellularity, including fibroblasts, lymphocytes, histiocytes and sm all blood vessels. In addition, in comedo DCIS, the lateral intercellular s paces between large myoepithelial cells that border the basal lamina are of ten expanded, compared to those of non-comedo DCIS. These results identify structural characteristics of comedo DCIS that may play a role in its great er preinvasive potential. They may also provide a structural basis for the different strategies that are needed for for clinical management of comedo DCIS, compared to non-comedo DCIS.